Thermal expansion behaviour of high performance PEEK matrix composites

The thermal expansion behaviour of high performance poly(ether-ether-ketone) (PEEK) composites reinforced with micro-(8 mu m) and nano- (39 nm) sized Al(2)O(3) particles was studied. The distribution of Al(2)O(3) in the PEEK matrix was studied by scanning electron microscopy and transmission electron microscopy. The coefficient of thermal expansion (CTE) was reduced from 58 x 10(-6) degrees C(-1) for pure PEEK to 22 x 10(-6) degrees C(-1) at 43 vol% micro-Al(2)O(3) and to 23 x 10(-6) degrees C(-1) at 12 vol% nano-Al(2)O(3) composites. For a given volume fraction, nano- Al(2)O(3) particles are more effective in reducing the CTE of composites than that of micro-Al(2)O(3) particles. This may be attributed to the much higher interfacial area or volume of nanocomposites than that of microcomposites. The upper limit and lower limit of the Schapery model separately fit closely the CTE of the micro- and nano-composites, respectively. Other models such as the rule of mixture and Kerner and Turner models were also correlated with the data.